This invention pertains to angiographic devices for injecting into a patient contrast media at a controlled rate and pressure during x-ray photography. More specifically, this invention is an improvement over commonly assigned, incorporated U.S. Pat. No. 4,006,736, which improvement concerns automated control of such angiographic injector devices being responsive to input information supplied by an operator to develop control signals for automatically controlling the injection process.
An angiographic injector is useful for controlling the delivery rate, amount, duration, and pressure of contrast media, usually a liquid iodine solution, injected into a patient. Such devices are used in x-ray photography to enhance the contrast of the image obtained thereby. In a typical operation of such device, an operator loads the same with a certain amount of contrast media, connects a delivery tube extending from a fluid reservoir of the device to a catheter placed in the vascular system of a patient, and then actuates the device by forcing the media into the blood stream while exposing the patient to x-rays during the photographic process. Among other things, it is very important that the proper amount of contrast media, as well as the pressure and rate at which it is delivered, be controlled accurately for safe and desirable results.
One such angiographic injector device over which the present invention is an improvement is described in U.S. Pat. No. 4,006,736 issued to Kranys et al, commonly owned by the assignee hereof. As with many other types of angiographic injector devices, this system is rather mechanical and although efficient, does not take advantage of certain potential automatic control and test features which can facilitate its use and reduce the likelihood of errors during its operation. As known, certain errors can be fatal or expose the patient to undue risks of harm.
As examples of potential capabilities under automated control, it is often desirable to provide multi-level injections during an x-ray photographing sequence. In this case, the contrast media is injected, for example, in step-wise changing flow rates and/or pressures. It is also desirable to provide multiphasic injections in which the programmed injection profile is delivered several times in succession under operator or remote control. Also, it may be desirable to automatically compute parameters involved in the injection of a specific amount of contrast media and to enable the size of the syringe to be changed without adversely affecting the operation of the injection and without requiring reprogramming. Such features are not known to exist with prior art devices. Moreover, certain mechanical control and electronic control features can be integrated to enhance reliability, such as by providing a mechanical stop member to prevent further movement of a syringe plunger when a predetermined amount of contrast media already has been injected. Additionally, rather than requiring the operator to calculate flow rates and/or volumes, this can automatically be computed by a processor controlled system as a function of an injection parameter supplied to the system by the operator, whereupon the system itself would then calculate the corresponding pressure and control signals for delivery of the media. Still further, the use of a microprocessor in an angiographic injector device enables various programming verification steps not otherwise available. These are only a few automatic control features which are not known to exist with prior art systems.
In view of the foregoing, it is a primary objective of the present invention to provide a processor-controlled angiographic injector device for automatically delivering contrast media at controlled rates, pressures or volumes, which rates and pressures or volumes are automatically calculated on the basis of injection parameters supplied thereto by a user.
It is an additional objective of the present invention to provide safety and/or control features which limit the injection pressure and/or delivery of contrast media when certain limits are exceeded, such as a pressure limit of contrast media in the syringe.
It is yet a further objective of the present invention to provide a mechanical stop mechanism for mechanically preventing the plunger of a syringe from further movement when a given amount of contrast media has been injected, wherein the stop position is automatically determined on the basis of injection information supplied to the device.
It is an additional objective of the present invention to interlock the operation of the mechanical stop mechanism and a plunger drive circuit of the injector device so that they alternate in operation to ensure that the drive circuit of the plunger does not operate until the drive circuit of the stop mechanism has completed its setting of the stop position.
Another objective of the present invention is to provide a multi-level injection sequence under processor control whereby the duration and/or injection rate and/or pressure may step-wise be changed during separate injection sequences, as well as to provide means for compensating the plunger drive rate and delivered pressure on the basis of syringe size during the injection process.
An additional objective of the present invention is to provide pre-programmed injection parameters stored in a memory which may conveniently be recalled instantly and to provide means for retaining the stored parameters in the memory in the event of power interruption to the device.
Another objective of the present invention is to provide a plurality of reliability features, such as parameter verification, self-calibration, and self-testing of the various components of the device in order to improve safety.
A yet further objective of the present invention is to provide means for providing messages from the angiographic injector to the operator, in human readable format.